| Work Detail |
The First Solar unit and Uppsala University have created the cell that achieved a maximum power conversion efficiency of 23.75%. The result was confirmed by the Fraunhofer ISE.
Swedish photovoltaic manufacturer First Solar European Technology Center AB, a unit of US thin-film solar module producer First Solar, and Uppsala University have unveiled a new solar cell based on copper-indium-gallium-diselenide (CIGS) technology. ).
First Solars European Technology Center was previously known as Evolar, a company founded in 2019 from now-insolvent CIGS thin film manufacturer Solibro. It was subsequently acquired by First Solar in May 2023. The company is focused on developing solutions, including manufacturing equipment, to commercialize tandem solar technology with perovskite thin films.
The new solar cell achieved a maximum power conversion efficiency of 23.75% and a certified efficiency of 23.64%, thus breaking the previous world record of 23.35% achieved in 2019 by the Japanese Solar Frontier. Germanys Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) confirmed the result.
“We achieved this by combining four different approaches,” lead author of the research Jan Keller told pv magazine . “We added a relatively high concentration of silver to the absorber and applied a hockey stick depth profile of gallium (Ga). “In addition, we tailored a post-deposition treatment (PDT) of rubidium fluoride (RbF) to the absorber composition and subjected it to prolonged illumination.”
These processes, according to the research team, managed to improve the microstructure, reduce the defect density and mitigate band gap fluctuations, passivate the absorber surface and increase the doping density. “Overall, this allowed us to reduce the open-circuit voltage deficit, which translated into a high external radiative efficiency of 1.6%,” Keller added.
Presented in the study “High-concentration silver alloying and steep back-contact gallium grading enabling copper indium gallium selenide solar cell with 23.6% efficiency,” recently published in Nature Energy , the cell was built with a molybdenum-coated glass substrate. (Mo), a sodium fluoride (NaF) layer, the CIGS absorber, the RbF layer, a cadmium sulfide (CdS) buffer layer, a zinc oxide (i-ZnO) window layer, an oxide film aluminum-doped zinc (ZnO:Al) and an anti-reflective coating based on magnesium fluoride (MgF2).
The scientists explained that they used a relatively high amount of silver in the absorber and placed a “hockey stick”-shaped gallium profile with a high Ga concentration near the back Mo contact and a lower, constant concentration in the region. closest to the CdS buffer layer. They also applied a standard post-deposition treatment (PDT) with RbF, which they said reduced the thickness of the CdS buffer layer to 25 nm.
“Our study demonstrates that CIGS thin film technology is a competitive alternative as a stand-alone solar cell. “The technology also has properties that can work in other contexts, such as the bottom cell of a tandem solar cell,” the research team stated.
Looking ahead, scientists say they could increase cell efficiency by over 25%. This would be achieved by avoiding parasitic absorption in the window and buffer layers, while maintaining the same levels of open circuit voltage and fill factor. “To exceed this level, we must continue to improve the quality of the absorber and reach external radiative efficiency (ERE) values ??much higher than 1.6% to further reduce the open circuit voltage deficit and the ideality factor,” they concluded. . |
